//
// Copyright (c) 2008-2011, Kenneth Bell
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//

using System;
using System.IO;
using System.Text;
using DiscUtils.Streams;

namespace DiscUtils.Udf
{
    internal static class UdfUtilities
    {
        private static readonly ushort[] CrcTable =
        {
            0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5, 0x60C6, 0x70E7,
            0x8108, 0x9129, 0xA14A, 0xB16B, 0xC18C, 0xD1AD, 0xE1CE, 0xF1EF,
            0x1231, 0x0210, 0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
            0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C, 0xF3FF, 0xE3DE,
            0x2462, 0x3443, 0x0420, 0x1401, 0x64E6, 0x74C7, 0x44A4, 0x5485,
            0xA56A, 0xB54B, 0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
            0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6, 0x5695, 0x46B4,
            0xB75B, 0xA77A, 0x9719, 0x8738, 0xF7DF, 0xE7FE, 0xD79D, 0xC7BC,
            0x48C4, 0x58E5, 0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
            0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969, 0xA90A, 0xB92B,
            0x5AF5, 0x4AD4, 0x7AB7, 0x6A96, 0x1A71, 0x0A50, 0x3A33, 0x2A12,
            0xDBFD, 0xCBDC, 0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
            0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03, 0x0C60, 0x1C41,
            0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD, 0xAD2A, 0xBD0B, 0x8D68, 0x9D49,
            0x7E97, 0x6EB6, 0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
            0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A, 0x9F59, 0x8F78,
            0x9188, 0x81A9, 0xB1CA, 0xA1EB, 0xD10C, 0xC12D, 0xF14E, 0xE16F,
            0x1080, 0x00A1, 0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
            0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C, 0xE37F, 0xF35E,
            0x02B1, 0x1290, 0x22F3, 0x32D2, 0x4235, 0x5214, 0x6277, 0x7256,
            0xB5EA, 0xA5CB, 0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
            0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447, 0x5424, 0x4405,
            0xA7DB, 0xB7FA, 0x8799, 0x97B8, 0xE75F, 0xF77E, 0xC71D, 0xD73C,
            0x26D3, 0x36F2, 0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
            0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9, 0xB98A, 0xA9AB,
            0x5844, 0x4865, 0x7806, 0x6827, 0x18C0, 0x08E1, 0x3882, 0x28A3,
            0xCB7D, 0xDB5C, 0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
            0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0, 0x2AB3, 0x3A92,
            0xFD2E, 0xED0F, 0xDD6C, 0xCD4D, 0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9,
            0x7C26, 0x6C07, 0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
            0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA, 0x8FD9, 0x9FF8,
            0x6E17, 0x7E36, 0x4E55, 0x5E74, 0x2E93, 0x3EB2, 0x0ED1, 0x1EF0
        };

        public static ushort ComputeCrc(byte[] buffer, int offset, int length)
        {
            ushort result = 0;

            for (int i = 0; i < length; ++i)
            {
                result = (ushort)(CrcTable[(result >> 8 ^ buffer[offset + i]) & 0xFF] ^ (result << 8));
            }

            return result;
        }

        public static DateTime ParseTimestamp(byte[] buffer, int offset)
        {
            bool allZero = true;
            for (int i = 0; i < 12; ++i)
            {
                if (buffer[i] != 0)
                {
                    allZero = false;
                    break;
                }
            }

            if (allZero)
            {
                return DateTime.MinValue;
            }

            ushort typeAndZone = EndianUtilities.ToUInt16LittleEndian(buffer, offset);

            int type = (typeAndZone >> 12) & 0x0F;
            int minutesWest = typeAndZone & 0xFFF;

            if ((minutesWest & 0x800) != 0)
            {
                minutesWest = (-1 & ~0xFFF) | minutesWest;
            }

            int year = ForceRange(1, 9999, EndianUtilities.ToInt16LittleEndian(buffer, offset + 2));
            int month = ForceRange(1, 12, buffer[offset + 4]);
            int day = ForceRange(1, 31, buffer[offset + 5]);
            int hour = ForceRange(0, 23, buffer[offset + 6]);
            int min = ForceRange(0, 59, buffer[offset + 7]);
            int sec = ForceRange(0, 59, buffer[offset + 8]);
            int csec = ForceRange(0, 99, buffer[offset + 9]);
            int hmsec = ForceRange(0, 99, buffer[offset + 10]);
            int msec = ForceRange(0, 99, buffer[offset + 11]);

            try
            {
                DateTime baseTime = new DateTime(year, month, day, hour, min, sec, 10 * csec + hmsec / 10,
                    DateTimeKind.Utc);
                return baseTime - TimeSpan.FromMinutes(minutesWest);
            }
            catch (ArgumentOutOfRangeException)
            {
                return DateTime.MinValue;
            }
        }

        public static string ReadDString(byte[] buffer, int offset, int count)
        {
            int byteLen = buffer[offset + count - 1];
            return ReadDCharacters(buffer, offset, byteLen);
        }

        public static string ReadDCharacters(byte[] buffer, int offset, int count)
        {
            if (count == 0)
            {
                return string.Empty;
            }

            byte alg = buffer[offset];

            if (alg != 8 && alg != 16)
            {
                throw new InvalidDataException("Corrupt compressed unicode string");
            }

            StringBuilder result = new StringBuilder(count);

            int pos = 1;
            while (pos < count)
            {
                char ch = '\0';

                if (alg == 16)
                {
                    ch = (char)(buffer[offset + pos] << 8);
                    pos++;
                }

                if (pos < count)
                {
                    ch |= (char)buffer[offset + pos];
                    pos++;
                }

                result.Append(ch);
            }

            return result.ToString();
        }

        public static byte[] ReadExtent(UdfContext context, LongAllocationDescriptor extent)
        {
            LogicalPartition partition = context.LogicalPartitions[extent.ExtentLocation.Partition];
            long pos = extent.ExtentLocation.LogicalBlock * partition.LogicalBlockSize;
            return StreamUtilities.ReadExact(partition.Content, pos, (int)extent.ExtentLength);
        }

        private static short ForceRange(short min, short max, short val)
        {
            if (val < min)
            {
                return min;
            }
            if (val > max)
            {
                return max;
            }

            return val;
        }

        private static byte ForceRange(byte min, byte max, byte val)
        {
            if (val < min)
            {
                return min;
            }
            if (val > max)
            {
                return max;
            }

            return val;
        }
    }
}